Sound reproducing apparatus



R. E. TOLERTON SOUND REPRODUCING APPARATUS March 29, 1938.

Filed Aug, 3, 1954 closed in the above patent.

Patented Mar. 29, 1938 UNITED STATES SOUND REPRODUCING APPARATUS Ray E. Tolerton, Fort Wayne, Ind., assigner to The Magnavox Company, Fort Wayne, Ind., a

corporation of Arizona Application August 3, 1934, Serial No. 738,302

7 Claims.

This invention relates to electrodynamic sound reproducing apparatus and more particularly to an improved supporting and centering means for the apex and actuating coil of a corneal diaphragm of the type commonly used with apparatus of this character.

An object of the invention is to provide a new and improved centering support or spider for the diaphragm and actuating coil of an electrodynamic sound reproducing device which can be secured directly to the magnetic field structure without the interposition of special supporting means.

Another object of the invention is to provide a new and novel coil centering and supporting spider for apparatus of the above character which is simple and practical in construction and eiiicient in operation.

In the past, where the diaphragm and actuating coil centering support has taken a symmetrical and annular form, it has been the practice to provide a separate supporting plate, upon which the coil centering support can be mounted. An example of such an arrangement is shown in Edwin S. Pridham, United States Patent Number 1,886,735, dated April 8, 1932, and assigned to the assignee of this application for patent. In this prior patent the diaphragm and coil centering support has inner and outer annular portions which are connected together by spirally disposed iiexible arms. The inner annular portion of this support is secured to the diaphragm assembly and the outer annular portion thereof is iixed upon an outwardly disposed flange, carried by a supporting plate, which is adjustably secured upon the magnetic field structure. In this way the supporting plate forms a continuous annular support about the diaphragm actuating coil, to which the outer portion of the diaphragm and coil centering support can be attached.

An .annular diaphragm and coil centering support is capable of providing a uniform flexibility throughout its circumference if its outer periphery is supported at uniformly spaced points, as dis- I-Iowever, the provision of a symmetrical support for a diaphragm when the support is disposed inside of the dia phragm.

Other objects and advantages of the invention will be in part pointed out and in part evident to those skilled in the art as the description thereof proceeds.

For a. better understanding of the invention reference should be had to the accompanying drawing wherein there are shown, by way of illustration and not of limitation, preferred embodiments thereof.

In the drawing;

Figure l is a fragmentary vertical sectional View taken along line I-I of Figure 3,

Figure 2 is a perspective View showing a son called outside centering spider of the type contemplated `by this invention,

Figure 3 is a fragmentary front elevation of a loud speaker with a portion of the diaphragm broken away to disclose the details of construction,

Figure 4 is a fragmentary sectional view showing a preferred manner of securing the centering spider to the magnetic eld structure,

Figure 5 is a perspective view of a clamping plate,

Figure 6 is a fragmentary sectional view showing the manner of attaching the actuating coil terminal leads. to the centering spider, and

Figure 7 is a View similar to Figure 1 showing :1;

the invention embodied in a so-called inside centering spider.

In the drawing the diaphragm supporting and centering spider, contemplated by this invention,

is shown as applied to an electrodynamic sound 2' reproducing device of the type having a truncated conical diaphragm which is adapted to be actuated by a cylindrical coil secured at the apex thereof. As here shown, the numerals Iii and I I designate respectively the inner and outer poles of a magnetic field structure. Secured upon the outer pole I I of the magnetic eld structure, there is a diaphragm supporting housing i2, to which the periphery of a conical diaphragm I3 is attached. At the apex of the diaphragm I3, there *7 is a cylindrical coil support i4 which carries a diaphragm actuating coil l5. The diaphragm actuating coil i5 is disposed in an air gap formed between the poles Iii and II and is adapted to move the diaphragm axially to reproduce sound when a source of modulated current is connected thereto.

In order to hold the cylindrical coil support I4 and the diaphragm actuating coil l5 concentric Within the air gap and at the same time permit a limited axial movement thereof, the diaphragm assembly, which includes the diaphragm I3, the cylindrical coil support I4 and the actuating coil I5, is provided at its small end with a flexible centering support or spider designated generally by the numeral I6.

As shown in Figure 2 of the drawing, the flexible centering support or spider I6, in its preferred form, has a rigid flat portion I 'I which is adapted to be secured upon the outer pole I I and a raised annular portion I8 that is secured to the diaphragm assembly. The raised annular portion I8 is formed integral with the rigid at portion I'I by pressing it outwardly therefrom so as to provide a continuous cylindrical connecting web portion or flange I9 therebetween. In addition to being pressed out, as above, the raised annular portion I8 is rendered flexible by cutting out portions thereof so as to provide a plurality of non-radial connecting arms 2D that extend between the cylindrical portion or flange I9 and a part 2| of the raised annular portion I8 which is adapted to engage the diaphragm' assembly.

For stiffness and to provide for a firm, gluing of the flexible centering support I6 to the diaphragm assembly, the part 2I of the raised annular portion I8 is provided with a flanged edge 22. The centering support or spider I6 will preferably be made in one piece and of material which can be easily molded or pressed into the configuration desired. 'Ihe material must also be of such a character that it will permanently hold its shape and not be broken by a frequent flexing of portions thereof when in operation. Such a material can be provided by impregnating a sheet of fabric with phenolic condensate. A sheet of this material can be formed, as above, while the phenolic condensate is plastic and then baked. After baking the device will possess the strength and flexibility required for a centering support of the character described. If the centering support I6 is formed of the above material and in the above manner, it will be necessary to rst form the rigid flat portion I'I with the raised annular portion I8 blank and then punch or cut out parts thereof to form the non-radial connecting arms which impart flexibility to the latter portion. The securing holes in the rigid flat portion I'I and the opening for the cylindrical coil support I4, defined by the flanged edge 22, may also be punched or cut out at the same time. In addition to the non-radial connecting arms 28, the raised annular portion I8 will be provided with a suitable extension 23, upon which terminals, for the ends of the coil I5, may be secured.

After the centering support or spider I6 has been formed and secured to the diaphragm assembly, as shown in Figure 1 of the drawing, it is positioned upon the end of the magnetic field structure, together with the diaphragm, and there secured, as shown in Figure 3 of the drawing, by means of four screws 24 which are preferably threaded into slightly raised bosses 25 formed upon the diaphragm supporting housing I2.

As illustrated in Figure 4 of the drawing, the provision of the bosses 25 upon the housing I2 avoids the necessity for drilling into the outer pole II. However, it is to be understood that the rigid flat portion I'I of the centering support I6 may be secured directly upon the outer pole II, if desired. In order to prevent a distortion or a twisting of the centering support or spider I6 by a tightening of any one of the screws 24,

there is an arcuate clamping plate 26 having a hole at each end, through which a screw 24 may pass. This clamping plate 26 is dished upwardly between its ends so that no rattle will be set up by a striking of the parts should the centering support I6 vibrate. A preferred form of clamping plate 26 ls shown in detail in Figure 5 of the drawing.

As shown in Figure 6 of the drawing, each end of' the diaphragm actuating coil I5 is brought out and soldered to a suitable metallic terminal 21, carried by the extension 23, formed upon the inner portion 2I of the centering support I6. Extending outwardly from each of the terminals 21 is a flexible lead 28 which connects through a terminal board (not shown) with a source of modulated current as, for instance, the output transformer of a radio set or a thermionic tube amplifier. 'I'he flexible lead 28 is bowed out slightly so as not to interfere with the free flexing of the non-radial connecting arms 20 and is securely fastened to the cylindrical portion or flange I9, of the centering support I6, by a suitable tie 29 which passes through small holes 30 formed therein.

With the above arrangement it will be seen that the cylindrical portion or flange I9, upon the rigid flat portion I'I, will form a rigid continuous circumferential support for the raised annular portion I8 and permit the non-radial connecting arms 20 to flex uniformly and hold the diaphragm actuating coil I5 concentric within the air gap under all conditions of operation. In other words, the rigid flat portion Il will be reinforced by the cylindrical portion or flange I9 so that no flexing will take place in the centering support or spider I6, except that which is provided for by the nonradial connecting arms 20.

While the invention has been described above in connection with a centering support or spider of the so-called outside type, it can also be embodied in a centering support or spider of the so-called inside type. An adaptation of the invention to a centering support or spider of this latter type is illustrated in Figure 7 of the drawing. In this figure of the drawing a diaphragm 3I is shown with an attached coil support 32 disposed between the poles I0 and II of the magnetic field structure. In this instance, the

diaphragm coil support 32 is held concentrically within the air gap by a flexible centering support or spider 33 which is secured directly upon the end of the pole I8, rather than upon an extension or abutment such as is customarily provided with a so-called inside flexible centering support. The flexible centering support 33 1s pressed or molded withA an integral inwardly extending cylindrical portion 34 that terminates with a flat end portion 35, through which a screw 36 is threaded into the pole I0. At its outer periphery the flexible centering support 33 has a circumferential flange 31 and located between the top of the cylindrical portion 34 and the circumferential flange 3'I there is a plurality of nonradial and flexible connecting arms 38. These connecting arms 36 may take any desired shape. For example, they can be like the arms 20 of the previously described centering support I6. With this latter type of centering support, the abutment which is usually turned upon the inner pole I0 may be dispensed with, and as a result the possibility of magnetic leakage at this point is eliminated.

Having thus described my invention, I desire to have it understood that this invention is not limited to the specific means disclosed, but may be embodied in other ways that Will suggest themselves to persons skilled in the art. It is belived that this invention is new and it is desired to claim it so that all such changes as come within the scope of the appended claims are to be considered as part of this invention.

Having thus described my invention, what I claim and desire to secure by Letters Patent isl. The combination of a. conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, and a unitary support for said diaphragm comprising a member of mouldable nonmetallic material having an outer at portion, an annular upstanding flange formed centrally thereupon, and a plurality of flexible arms extending inwardly from the top of said flange and forming an axially yielding support for the small end of the conical diaphragm.

2. The combination of a conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, and a support for said diaphragm and actuating coil comprising a single member of hot pressed mouldable material having an outer flat portion, an upstanding cylindrical ange formed centrally thereupon, and an inner iiat portion extending from the top of said flange and having a plurality of flexible arms forming a means for axially centering the small end of a conical diaphragm and the actuating coil.

3. A centering support for a conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, comprising an integrally formed member of non-metallic mouldable material having an outer support engaging portion extending in a plane transverse to the axis of the diaphragm, and an inner diaphragm engaging portion formed in a plane parallel with but displaced from the plane of said outer support engaging portion, said outer and inner portions being connected together by a cylindrical connecting web formed therebetween and extending concentric to the axis of the diaphragm.

4. A centering support for a conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, comprising a unitary member of thermoplastic material having a flat portion disposed in one plane adapted to engage a supporting means adjacent the cylindrical actuating coil, and a second ilat portion formed in a plane displaced axially from but parallel With the plane of said rst portion having flexible arms adapted to be secured to the diaphragm, said iiat portions being formed concentrically With respect to each other upon opposite sides and at opposite ends of an integrally formed cylindrical connecting Web.

5. A centering support for a conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, comprising a centering member constructedin one piece of a mouldable nonmetallic material having a rigid cylindrical portion adapted to be disposed concentric to the axis of the diaphragm, a transversely extending portion of ilexible configuration at one end of said rigid cylindrical portion adapted to engage the diaphragm, adjacent its actuating coil, and a second transversely extending portion at the other end of said cylindrical portion extending in a plane parallel with said flexible portion and adapted to be secured upon a fixed support.

6. A centering support for a conical diaphragm of the type having a cylindrical actuating coil at the apex thereof, comprising an integral member of mouldable phenolic condensate having an integrally formed cylindrical reenforcing portion adapted to be secured concentric to the axis of the diaphragm, outwardly extending portions at one end of said cylindrical portion adapted to secure said cylindrical portion upon a fixed support, a web of said mouldable material across the other end of said cylindrical portion having parts cut away to form iiexible arms, and a cylindrical iiange formed upon said web concentric with said reenforcing portion adapted to be secured to the diaphragm adjacent its actuating coil.

7. In a loudspeaker the combination of a magnetic eld frame having an annular air gap therein, a conical diaphragm supported upon said field frame having a coil at the small end thereof disposed in said air gap, and a support for centering said iield coil in said air gap comprising a onepiece non-metallic member having concentric transversely extending portions disposed in spaced parallel planes and connected together by a cylindrical portion extending concentric to the axis of the diaphragm, one of said concentric transversely extending portions being adapted to be secured upon the magnetic field frame, the other of said concentric transversely extending portions being located in outwardly spaced relation from said field frame engaging portion and adapted to be secured to the diaphragm.

RAY E. TOLERTON. 

